The disclosed embodiments relate to a medical device. Specifically, the disclosed embodiments relate to a stent delivery system for delivering a stent stored in a catheter to a target site with a pusher guide wire.
Stents are medical devices used at the site of a stenosis or an occlusion created to treat an aneurysm (hereinafter referred to as a “target site”) formed in a blood vessel or a digestive organ. For example, a stent may be used for supporting the lumen of a blood vessel or a digestive organ so that the blood vessel or the digestive organ, which is expanded with a balloon catheter, will not be affected with stenosis again. Further, a stent may be used for confining an embolization coil in an aneurysm formed in an arterial blood vessel of the abdomen or the brain to prevent the aneurysm from rupturing.
Stents are generally classified into two categories: a balloon-expandable stent, which is expandable with a balloon catheter, and a self-expandable stent in which the stent expands spontaneously when no longer constrained. Recently, self-expandable stents that are resistant to deformation even when subjected to external force have been often used.
Known stent delivery systems for delivering a stent stored inside a catheter to a target site include a system in which an anchor member provided in a stent is disposed within a gap formed between a middle columnar member and a proximal end columnar member in order to push the stent in the distal direction (for example, see Japanese Patent No. 4574131). In another known stent delivery system, a metal ring is separately provided at the outer periphery of a coil body of a pusher guide wire in order to push a stent in the distal direction (for example, see Japanese Patent Laid-Open Application No. 2013-521022). However, there are problems with each of these stent delivery systems.
As discussed above, the proximal end columnar member of Japanese Patent No. 4574131 can contact the anchor member to deliver the stent in the distal direction when an operator pushes the pusher guide wire in the distal direction. However, the rotating force of the pusher guide wire is difficult to transmit to the distal end of the pusher guide wire when the operator rotates the pusher guide wire, because the middle columnar member is separate from the proximal end columnar member. As a result, it is difficult to precisely release the stent at the target site (in other words, the stent is easily anteroposteriorly dislocated from the target site).
Further, there has been the following problem with the stent delivery system according to Japanese Patent Laid-Open Application No. 2013-521022. Although the rotating force exerted by an operator can be transmitted to the distal end of the pusher guide wire since the coil body of the pusher guide wire is formed as one integral part extending toward the distal end, the flexibility of the pusher guide wire is impaired since the metal ring for pushing the stent in the distal direction is separately provided. In particular, the metal ring may get caught within the catheter when the stent delivery system is inserted into a curved blood vessel or digestive organ, making it difficult to deliver the stent to the target site.